When it comes to GPS, most people are quite familiar with it. Meanwhile, China's domestic positioning service, BeiDou (BDS), has emerged as a new player and has now become a leader in global positioning systems. GPS/BDS, along with Europe's Galileo system and GLONASS, currently represent the four most widely used positioning services, supporting a wide range of civilian and military applications. This article briefly explores the core principles of these positioning services.

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The Core Data Source for Positioning

First, it’s important to understand where the core data for positioning comes from. Of course, it’s from satellites—specifically, positioning satellites. In order for a device to determine its position, it must receive data from at least four satellites at the same time. Why is that? The key lies in distance calculation. Positioning satellites orbiting in space are constantly broadcasting their position, coordinates, and other key information. GPS chips serve as the main tools for receiving this information, decoding it, and organizing the data for use.

The Importance of Time in Satellite Broadcast Data

Next, let’s look at why the core of the satellite’s broadcast data is time. The satellites use highly accurate atomic clocks to ensure synchronization within the positioning system. When a GPS device knows the time, it can calculate a crucial piece of information—time difference. By subtracting the time the signal was sent (as indicated in the satellite's broadcast) from the device’s own time, we get the time taken for the signal to travel from the satellite. Since electromagnetic waves travel at the speed of light, multiplying this time difference by the speed of light gives the distance between the device and the satellite.

Converting Distance Data to Coordinates

Now, how is this distance data translated into actual coordinates? As mentioned earlier, at least four satellite signals are needed to calculate the device’s location. In three-dimensional space, each satellite can be considered a point, and knowing both its position and the distance from it, the device can be at any point on a sphere centered on the satellite. The second, third, and fourth satellites add additional spheres, and where these spheres intersect, you get the device’s position. Therefore, at least four satellites are required to calculate the device’s three-dimensional coordinates accurately. However, it’s best to receive data from more satellites to account for errors. Even with the highest precision clocks, there will still be slight inaccuracies, including errors in satellite positions, transmission speed variations due to the Earth's ionosphere, and delays caused by GPS device time synchronization. These errors can compound in the calculations, so additional satellite data is used to correct them.

The Rise of BeiDou

Reflecting on BeiDou's rise, we recall the infamous "Galaxy Incident" on July 7, 1993, when a Chinese vessel lost GPS service, causing it to drift aimlessly in the Indian Ocean. After enduring humiliation under U.S. pressure, it was only after agreeing to ship inspections that the vessel was allowed to return. Following this, China sought cooperation with Europe’s Galileo system, but this partnership was short-lived, eventually ending in failure due to shifting European politics and U.S. pressure. Despite this setback, China didn’t give up. Satellite after satellite was launched, and technology improved step by step. Today, the BeiDou system has not only caught up but has surpassed many others. In optimal signal conditions, its positioning accuracy can reach as high as 0.5 meters, making it the most accurate global positioning system.

Lastly, we would like to introduce our GPS positioning modules and RS485 devices, which can directly output processed latitude and longitude data through serial ports or 485-modbus access. These devices provide easy access to positioning, time, heading, and speed information.